Stewie from Family Guy is UltronianThe Ultronian Superhero, Thermoman, from My Hero. It's common fact that various elements from TV, film and other media exists in the Family Guy Universe, so what about Thermoman. As seen in My Hero, Thermoman, also known by his Human of alias of George Sunday the Irish Shopkeeper, has two children who, being Ultronian, are able to talk, and have Superpowers. Six days (that's the length of Ultronian pregnancy) before Stewie was born, Thermoman met Lois and they had a one-night stand, concieving Stewie. Thermoman left right after and Lois kept Peter in the dark about it, so he thinks that he is Stewie's father. As Lois said when she dreamt of finding out Stewie was evil, she smoked pot when she was pregnant with him. This stunted his development, so he doesn't have advanced Superhero powers (e.g. flying, thermobreath), but he could still talk, walk, have super-intelligence and even the ability to slap around human adults.
Tyler is an UltronianTyler is an exiled Ultronian, possibly a past villain or ruler who was deposed. The mind wipe on him was successful (being done by the best science Ultron has) but he retains his abilities to recognize aliens and other Ultronians for who they really are. His memories of being in space and meeting fantastic aliens and people are really just that, fragments of his true memories from before his mind got wiped. This explains also how George (Thermoman) cannot truly wipe Tyler's brain because he is of the same race. Thermoman himself may know what/who Tyler is but doesn't say anything so as not to upset Janet. It also explains why Thermoman tolerates Tyler so well, letting him hang around, even living next door to him... he's keeping an eye on Tyler to make sure he doesn't revert to what he once was.
Ultronians are related to Time LordsThey are much older than they look can change their entire bodies in certain circumstances, and have two hearts. They aren't the same species though but it's a bit like Homo Sapiens and Neanderthals.